First, thank you for creating this plugin! It gave me exactly what I needed for a complex WP child theme I'm creating for a client.

The Problem:
I am using Custom Widget Area to add MegaMenu to my header. Works really good... however...

In checking my site with validator.w3.org it gives the following error for this plugin. This is because in custom_widget_area.php when your plugin registers as a sidebar widget you used an li for the "before_widget" and "after_widget" tag. This also gives a list item "dot" at the beginning of the menu when used in the header.

Also, that beginning li gave me a "stray dot" at the beginning of my header menu and it caused extra space above the menu in Chrome and IE.

What I did was change this the li to a div in both places. Please consider making this same change to your plugin so others don't have similar problems.